Tucked active region without dummy poly for performance boost and variation reduction

ABSTRACT

In one embodiment, a semiconductor device is provided that includes a semiconductor substrate including an active region and at least one trench isolation region at a perimeter of the active region, and a functional gate structure present on a portion of the active region of the semiconductor substrate. Embedded semiconductor regions are present in the active region of the semiconductor substrate on opposing sides of the portion of the active region that the functional gate structure is present on. A portion of the active region of the semiconductor substrate separates the outermost edge of the embedded semiconductor regions from the at least one isolation region. Methods of forming the aforementioned device are also provided.

BACKGROUND

The present disclosure relates to semiconductor structures and methodsof fabricating such semiconductor structures. More particularly, thepresent disclosure relates to semiconductor structures that includeembedded semiconductor regions.

For more than three decades, the continued miniaturization of siliconmetal oxide semiconductor field effect transistors (MOSFETs) has driventhe worldwide semiconductor industry. Various showstoppers to continuedscaling have been predicated for decades, but a history of innovationhas sustained Moore's Law in spite of many challenges. However, thereare growing signs today that metal oxide semiconductor transistors arebeginning to reach their traditional scaling limits. Since it has becomeincreasingly difficult to improve MOSFETs and therefore complementarymetal oxide semiconductor (CMOS) performance through continued scaling,further methods for improving performance in addition to scaling havebecome critical.

SUMMARY

A method of forming a semiconductor device is provided that includesproviding a semiconductor substrate including an active region and atleast one trench isolation region at a perimeter of the active region. Aplurality of replacement gate structures are formed on the active regionof the semiconductor substrate, wherein an interface replacement gatestructure of the plurality of replacement gate structures is formed onan interface between the active region and the at least one trenchisolation region, and at least one device replacement gate structure ofthe plurality of replacement gate structures is formed on a portion ofthe active region that is separated from the at least one trenchisolation region. Embedded semiconductor regions are formed in theactive region of the semiconductor substrate between adjacentreplacement gate structures of the plurality of replacement gatestructures. The device replacement gate structure is replaced with afunctional gate structure. At least a portion of the interfacereplacement gate structure is removed.

A method of forming a semiconductor device is provided that includesproviding a semiconductor substrate including an active region and atleast one trench isolation region at a perimeter of the active region.At least one functional gate structure is formed on the active region ofthe semiconductor substrate and an interface replacement gate structureis formed on an interface between the active region and the at least onetrench isolation region. The interface replacement gate structureincludes a gate stack of a sacrificial gate conductor structure and agate dielectric, and spacers adjacent to the gate stack. Embeddedsemiconductor regions are formed in the active region of thesemiconductor substrate between the portion of the active region thatthe functional gate structure is present on and the portion of theactive region at the interface with the at least one trench isolationregion that the replacement gate structure is present on. Source regionsand drain regions are formed on opposing sides of the portion of thesubstrate that the device gate structure is formed on. At least thesacrificial gate conductor structure of the interface replacement gatestructure is removed.

In another aspect, a semiconductor device is provided. In oneembodiment, the semiconductor device includes a semiconductor substrateincluding an active region and at least one trench isolation region at aperimeter of the active region. A functional gate structure is presenton a portion of the active region of the semiconductor substrate.Embedded semiconductor regions are present in the active region of thesemiconductor substrate on opposing sides of the portion of the activeregion that the functional gate structure is present on, wherein aportion of the active region of the semiconductor substrate separatesthe outermost edge of the embedded semiconductor regions from the atleast one isolation region.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example and notintended to limit the disclosure solely thereto, will best beappreciated in conjunction with the accompanying drawings, wherein likereference numerals denote like elements and parts, in which:

FIG. 1 is a side cross-sectional view of forming a plurality ofreplacement gate structures on a semiconductor substrate including anactive region and at least one trench isolation region at a perimeter ofthe active region, in accordance with one embodiment of the presentdisclosure.

FIG. 2 is a side cross-sectional view of forming embedded semiconductorregions in the active region of the semiconductor substrate betweenadjacent replacement gate structures of the plurality of replacementgate structures, in accordance with one embodiment of the presentdisclosure.

FIG. 3 is a side cross-sectional view of removing a device replacementgate structure of the plurality of gate structures to provide an openingto an exposed portion of the active region of the semiconductorsubstrate, while the interface replacement gate structures of theplurality of gate structures are protected by a first photoresist mask,in accordance with one embodiment of the present disclosure.

FIG. 4 is a side cross-sectional view depicting forming a functionalgate structure, in accordance with one embodiment of the presentdisclosure.

FIG. 5 is a side cross-sectional view depicting a second photoresistmask over the functional gate structure, in accordance with oneembodiment of the present disclosure.

FIG. 6 is a side cross-sectional view depicting removing a sacrificialgate conductor structure of the interface replacement gate structures,in accordance with one embodiment of the present disclosure.

FIG. 7 is a side cross-sectional view depicting removing the spacers andgate dielectric of the interface replacement gate structures, inaccordance with one embodiment of the present disclosure.

FIGS. 8a-8b are side cross-sectional views depicting a semiconductordevice including a functional gate structure present on an active regionof a semiconductor substrate, wherein the source and drains regions ofthe device are present in embedded semiconductor regions, in which aportion of the active region separates the embedded semiconductorregions from the trench isolation regions, in accordance with oneembodiment of the present disclosure.

FIG. 9 is a side cross-sectional view depicting forming a functionalgate structure on the active device region of a semiconductor substrate,and forming an interface gate first structure over an interface betweenthe active region and at least one trench isolation region, inaccordance with one embodiment of the present disclosure.

FIG. 10 is a side cross-sectional view depicting forming embeddedsemiconductor regions in the active region of the semiconductorsubstrate depicted in FIG. 9, in accordance with one embodiment of thepresent disclosure.

FIG. 11 is a side cross-sectional view depicted forming a photoresistmask over the functional gate structure.

FIG. 12 is a side cross-sectional view depicting removing at least aportion of the interface gate structure, in accordance with oneembodiment of the present disclosure.

DETAILED DESCRIPTION

Detailed embodiments of the present disclosure are described herein;however, it is to be understood that the disclosed embodiments aremerely illustrative of the present disclosure that may be embodied invarious forms. In addition, each of the examples given in connectionwith the various embodiments of the disclosure are intended to beillustrative, and not restrictive. Further, the figures are notnecessarily to scale, some features may be exaggerated to show detailsof particular components. Therefore, specific structural and functionaldetails disclosed herein are not to be interpreted as limiting, butmerely as a representative basis for teaching one skilled in the art tovariously employ the present disclosure.

References in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed. For purposes of the description hereinafter, the terms“upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”,“bottom”, and derivatives thereof shall relate to the invention, as itis oriented in the drawing figures. The terms “overlying”, “atop”,“positioned on”, “present on” or “positioned atop” means that a firstelement, such as a first structure, is present on a second element, suchas a second structure, wherein intervening elements, such as aninterface structure, e.g. interface layer, may be present between thefirst element and the second element. The term “direct contact” meansthat a first element, such as a first structure, and a second element,such as a second structure, are connected without any intermediaryconducting, insulating or semiconductor layers at the interface of thetwo elements.

Semiconductor device performance enhancements, such as increased chargecarrier speed, may be provided by introducing a stress, e.g., tensile orcompressive stress, to the channel region of the semiconductor device,e.g., n-type or p-type field effect transistor (FET). The stress may beinduced to the channel region of a FET by positioning a well trenchcomposed of a stress inducing material, i.e., embedded semiconductorregion, adjacent to the channel region of the FET. It has beendetermined that contact by the embedded semiconductor region to theisolation region results in faceting of the material within the embeddedsemiconductor region. Facetting within the embedded semiconductor regionmay result in device variation, because of of a stress loss as well asdoping depth change. In one embodiment, the methods and structuresdisclosed herein reduce or substantially eliminate faceting of theembedded semiconductor region, by forming a replacement gate structureover the interface between the active region of the semiconductorsubstrate and the isolation region, e.g., trench isolation region, priorto forming the embedded semiconductor region. By forming the replacementgate structure over the interface between the active region and thetrench isolation region, the subsequently formed embedded semiconductorregion is separated from the trench isolation region, which reduces orsubstantially eliminates faceting in the embedded semiconductor region.

As used herein, a “semiconductor device” is an intrinsic semiconductormaterial that has been doped, i.e., into which a doping agent has beenintroduced, giving it different electrical properties than the intrinsicsemiconductor. Doping involves adding dopant atoms to an intrinsicsemiconductor, which changes the electron and hole carrierconcentrations of the intrinsic semiconductor at thermal equilibrium.The doping of the source and drain regions of the semiconductor devicedictate the conductivity type of the semiconductor device. As usedherein, the term “conductivity type” denotes a semiconductor devicehaving a p-type or n-type conductivity. In one embodiment, thesemiconductor device that is provided by the present disclosure is afield effect transistor. A field effect transistor is a semiconductordevice in which output current, i.e., source-drain current, iscontrolled by the voltage applied to a gate structure. A field effecttransistor has three terminals, i.e., a functional gate structure, asource region and a drain region. The functional gate structure controlsoutput current, i.e., flow of carriers in the channel, of asemiconducting device, such as a field effect transistor, throughelectrical or magnetic fields. The channel is the region between thesource region and the drain region of a semiconductor device thatbecomes conductive when the semiconductor device is turned on. A p-typeconductivity semiconductor device, such as a pFET, is a semiconductordevice in which the source and drain regions of the device are dopedwith a p-type dopant. An n-type conductivity semiconductor device, suchas an nFET, is a semiconductor device in which the source and drainregions of the device are doped with an n-type dopant.

FIG. 1 depicts forming a plurality of replacement gate structures on asemiconductor substrate including an active region and at least onetrench isolation region at a perimeter of the active region. Thesemiconductor substrate 5 may be composed of a Si-containing material.The term “Si-containing” is used herein to denote a material thatincludes silicon. Illustrative examples of Si-containing materialsinclude, but are not limited to: Si, SiGe, SiGeC, SiC, polysilicon,i.e., polySi, epitaxial silicon, i.e., epi-Si, amorphous Si, i.e., α:Si,and multi-layers thereof. Although silicon is the predominantly usedsemiconductor material in wafer fabrication, alternative semiconductormaterials can be employed, such as, but not limited to, germanium,gallium arsenide, gallium nitride, cadmium telluride and zinc sellenide.Although the semiconductor substrate 5 is depicted as a bulk-Sisubstrate, semiconductor on insulator (SOI) substrates have also beencontemplated and are within the scope of the present disclosure.

An active region is located within the semiconductor substrate 5 and hasa perimeter defined by an isolation region, such as a trench isolationregion 10. In one example, in which the semiconductor device formed onthe semiconductor substrate 5 is an n-type field effect transistor(nFET), the active region is doped to a p-type conductivity. In oneexample, in which the semiconductor device formed on the semiconductorsubstrate 5 is a p-type field effect transistor (nFET), the activeregion is doped to an n-type conductivity.

The isolation regions, e.g., trench isolation region 10, may compriseany of several dielectric isolation materials. Non-limiting examplesinclude oxides, nitrides and oxynitrides, particularly of silicon, butoxides, nitrides and oxynitrides of other elements are not excluded. Inone embodiment, the trench isolation region 10 primarily comprises anoxide of silicon. In one embodiment, the trench isolation region 10 isformed by forming a trench in the semiconductor substrate 5 utilizing adry etching process, such as reactive-ion etching (RIE) or plasmaetching, and then filling the trench with an insulating material, suchas an oxide. In one embodiment, the trench may be filled using adeposition method, such as chemical vapor deposition (CVD).

FIG. 1 further depicts forming a plurality of replacement gatestructures 15, 20 on a portion of a semiconductor substrate 5. At leastone replacement gate structure 15 may be formed over the interfacebetween the active region of the semiconductor substrate 5 and thetrench isolation region 10, and is hereafter referred to as an“interface replacement gate structure” (identified by reference number15). At least one of the replacement gate structure 20 is present over aportion of the active region that is subsequently processed to provide asemiconductor device, and is hereafter referred to as a “devicereplacement gate structure” (identified by reference number 20). Thedevice replacement gate structure 20 includes a sacrificial materialthat defines the geometry of later formed functional gate structuresthat function to switch the semiconductor device from an “on” to “off”state, and vice versa. Each of the replacement gate structures 15, 20may be composed of a sacrificial gate conductor structure 14, 19, a gatedielectric 13, 18, and a spacer 12, 17.

The gate dielectric 13, 18 may be formed in direct contact with theupper surface of the active region of the semiconductor substrate 5. Thegate dielectric 13, 18 may be composed of any dielectric material, suchas an oxide, nitride or oxynitride dielectric. In one embodiment, thegate dielectric 13, 18 may be composed of a high-k material. The term“high-k” denotes a material having a dielectric constant that is greaterthan the dielectric constant of silicon oxide at room temperature (20°C. to 25° C.), and atmospheric pressure (1 atm). For example, in oneembodiment, the dielectric constant of the gate dielectric 13, 18 isgreater than 4.0. In another embodiment, the high-k gate dielectric iscomprised of a material having a dielectric constant greater than 10.0.In yet another embodiment, the high-k gate dielectric layer is comprisedof a material having a dielectric constant ranging from 10 to 30.

Some examples of high-k dielectric materials suitable for the gatedielectric 13, 18 include hafnium oxide, hafnium silicon oxide, hafniumsilicon oxynitride, lanthanum oxide, lanthanum aluminum oxide, zirconiumoxide, zirconium silicon oxide, zirconium silicon oxynitride, tantalumoxide, titanium oxide, barium strontium titanium oxide, barium titaniumoxide, strontium titanium oxide, yttrium oxide, aluminum oxide, leadscandium tantalum oxide, lead zinc niobate and combinations thereof. Inone example, the gate dielectric 13, 18 is hafnium oxide (HfO₂).

In one embodiment, the gate dielectric 13, 18 is formed using adeposition process, such as chemical vapor deposition (CVD). Chemicalvapor deposition (CVD) is a deposition process in which a depositedspecies is formed as a result of chemical reaction between gaseousreactants at an elevated temperature (typically being greater than 200°C.), wherein solid product of the reaction is deposited on the surfaceon which a film, coating, or layer of the solid product is to be formed.Variations of chemical vapor deposition (CVD) processes for depositingthe gate dielectric 13, 18 include, but are not limited to, AtmosphericPressure CVD (APCVD), Low Pressure CVD (LPCVD) and Plasma Enhanced CVD(PECVD), Metal-Organic CVD (MOCVD) and others. In another embodiment,the gate dielectric 13, 18 may be formed by a thermal growth processsuch as, for example, oxidation, nitridation or oxynitridation. The gatedielectric 13, 18 has a thickness that ranges from 0.5 nm to 10 nm. Inanother embodiment, the gate dielectric 13, 18 has a thickness thatranges from 1 nm to 5 nm.

In one embodiment, when the gate dielectric 13, 18 is composed of ahigh-k dielectric, such as a Hf-containing dielectric, prior to formingthe gate dielectric 13, 18, an interfacial dielectric layer (not shown)can be formed on the exposed portion of the semiconductor substrate 5.The interfacial dielectric layer can be provided by thermal oxidation.In one embodiment, thermal oxidation of silicon can be performed in thepresence of oxygen at a temperature between 800° C. and 1200° C. In someexamples, the oxidant may be either water vapor (steam) or molecularoxygen. In another embodiment, the interfacial dielectric layer is anoxide that is formed using deposition. In some embodiments, theinterfacial dielectric layer is composed of silicon oxide and has athickness that ranges from 1 nm to 5 nm.

In one embodiment, the sacrificial gate conductor structure 14, 19 maybe composed of a semiconductor-containing material, such as asilicon-containing material. Silicon-containing materials that aresuitable for the sacrificial gate conductor structure 14, 19 include,but are not limited to, silicon (Si), single crystal silicon,polycrystalline silicon, amorphous silicon, SiO₂, Si₃N₄, SiO_(x)N_(y),SiC, SiCO, SiCOH, and SiCH compounds, and the above-mentionedsilicon-containing materials with some or all of the Si replaced by Ge.In one example, the sacrificial material that provides the sacrificialgate conductor structure 14, 19 is amorphous silicon.

The sacrificial material layer that provides the sacrificial gateconductor structure 14, 19 may be formed on the gate dielectric 13, 18using a deposition process, such as chemical vapor deposition (CVD).Variations of CVD processes include, but not limited to, AtmosphericPressure CVD (APCVD), Low Pressure CVD (LPCVD) and Plasma Enhanced CVD(EPCVD), Metal-Organic CVD (MOCVD) and combinations thereof may also beemployed. The sacrificial gate conductor structure 14, 19 may also bedeposited using evaporation, chemical solution deposition, spin ondeposition, and physical vapor deposition (PVD) methods.

In some embodiments, the material layers for the gate dielectric 13, 18and the sacrificial gate conductor structure 14, 19 may be depositedusing blanket deposited to form layered structure. Following deposition,the material layers for the gate dielectric 13, 18 and the sacrificialgate conductor structure 14, 19 may be patterned and etched to providethe replacement gate stack. Specifically, and in one example, a patternis produced by applying a photoresist to the surface to be etched,exposing the photoresist to a pattern of radiation, and then developingthe pattern into the photoresist utilizing a resist developer. Once thepatterning of the photoresist is completed, the sections covered by thephotoresist are protected, while the exposed regions are removed using aselective etching process that removes the unprotected regions. As usedherein, the term “selective” in reference to a material removal processdenotes that the rate of material removal for a first material isgreater than the rate of removal for at least another material of thestructure to which the material removal process is being applied. Insome examples, the selectivity may be greater than 100:1.

In one embodiment, the etch process removes the exposed portions of thesacrificial material layer with an etch chemistry that is selective tothe semiconductor substrate 5. In one embodiment, the etch process thatforms the replacement gate structures is an anisotropic etch. Ananisotropic etch process is a material removal process in which the etchrate in the direction normal to the surface to be etched is greater thanin the direction parallel to the surface to be etched. The anisotropicetch may include reactive-ion etching (RIE). Other examples ofanisotropic etching that can be used at this point of the presentdisclosure include ion beam etching, plasma etching or laser ablation.The width W1 of each of the replacement gate stack may range from 20 nmto 250 nm. In another embodiment, the width W1 of each of thereplacement gate stacks may range from 50 nm to 150 nm. In yet anotherembodiment, the width W1 of the each of the replacement gate stacks mayrange from 80 nm to 100 nm.

Still referring to FIG. 1, a spacer 12, 17 may be formed abutting thesidewall surfaces of the replacement gate stack. In some embodiments,each of the replacement gate structures 15, 20 include a gate dielectric13, 18, a sacrificial gate conductor structure 14, 19, and a spacer 12,17. In some embodiments, the spacer 12, 17 may be omitted, so that thereplacement gate structures 15, 20 include only the gate dielectric 13,18, and the sacrificial gate conductor structure 14, 19. The spacer 12,17 may be composed of an oxide, nitride or oxynitride. In one example,the spacer 12, 17 may be composed of silicon oxide (SiO₂). In yetanother embodiment, the spacer 12, 17 may be composed of silicon nitride(Si₃N₄). Other examples of materials suitable for the spacer 12, 17include organosilicate glass (OSG), fluorine doped silicon dioxide,carbon doped silicon dioxide, porous silicon dioxide, porous carbondoped silicon dioxide, spin-on organic polymeric dielectrics (e.g.,SILK™), spin-on silicone based polymeric dielectric (e.g., hydrogensilsesquioxane (HSQ) and methylsilsesquioxane (MSQ), and combinationsthereof. The spacer 12, 17 may be formed by deposition and etching.

FIG. 2 depicts forming embedded semiconductor regions 25 in the activeregion of the semiconductor substrate 5 between adjacent replacementgate structures 15, 20. The embedded semiconductor regions 25 may beformed by etching a trench into the active region of the semiconductorsubstrate 5. Because the interface replacement gate structure 15 ispresent over a portion of the active region of the semiconductorsubstrate 5 that is in contact with the trench isolation region 10, andthe trench is formed using an anisotropic etch, the embeddedsemiconductor regions 25 have an outermost edge E1 that is separatedfrom the trench isolation region 10 by a remaining portion 6 of theactive region of the semiconductor substrate 5. The remaining portion 6of the active region of the semiconductor substrate 5 is the portion ofthe semiconductor substrate 5 that is protected by the interfacereplacement gate structure 15 during the etch process that forms thetrench for the embedded semiconductor regions 25.

FIG. 2 depicts some embodiments of etching well trenches into the activeregion of the semiconductor substrate 5 on opposing sides of the devicereplacement gate structure 20. The etch process for forming the welltrenches may be an anisotropic etch. As used herein, an “anisotropicetch process” denotes a material removal process in which the etch ratein the direction normal to the surface to be etched is greater than inthe direction parallel to the surface to be etched. The anisotropic etchmay include reactive-ion etching (RIE). Reactive Ion Etching (RIE) is aform of plasma etching in which during etching the surface to be etchedis placed on the RF powered electrode. Moreover, during RIE the surfaceto be etched takes on a potential that accelerates the etching speciesextracted from plasma toward the surface, in which the chemical etchingreaction is taking place in the direction normal to the surface. Otherexamples of anisotropic etching that can be used at this point of thepresent disclosure include ion beam etching, plasma etching or laserablation.

The well trenches may have a width W2 ranging from 40 nm to 200 nm. Inanother embodiment, the well trenches have a width W2 ranging from 50 nmto 100 mm. The depth D1 of the well trenches may range from 5 nm to 50nm. In another embodiment, the depth of the well trenches may range from15 nm to 30 nm. The remaining portion 6 of the active region thatseparates the well trenches from the trench isolation regions 10 mayhave a width W3 that ranges from 5 nm to 50 nm. In another embodiment,the remaining portion 6 of the active region that separates the welltrenches from the trench isolation regions 10 may have a width W3 thatranges from 10 nm to 30 nm.

Still referring to FIG. 2, the embedded semiconductor regions 25 maythen be formed in the well trenches. By “embedded” it is meant that atleast a portion of the embedded semiconductor region 25 is present belowthe upper surface of the semiconductor substrate 5. In some embodiments,greater than 75% of the embedded semiconductor region 25 is presentbelow the upper surface of the semiconductor substrate 5. In yet anotherembodiment, greater than 90% of the embedded semiconductor region 25 ispresent below the upper surface of the semiconductor substrate 5. In oneexample, the entirety of the embedded semiconductor region 25 is presentbelow the upper surface of the semiconductor substrate 5.

In one embodiment, the embedded semiconductor regions 25 may beepitaxially formed in the well trenches. “Epitaxially growing, epitaxialgrowth and/or deposition” mean the growth of a semiconductor material ona deposition surface of a semiconductor material, in which thesemiconductor material being grown has the same crystallinecharacteristics as the semiconductor material of the deposition surface.When the chemical reactants are controlled and the system parameters setcorrectly, the depositing atoms arrive at the deposition surface withsufficient energy to move around on the surface and orient themselves tothe crystal arrangement of the atoms of the deposition surface. Thus, anepitaxial film deposited on a {100} crystal surface will take on a {100}orientation. If, on the other hand, the wafer surface has an amorphoussurface layer, possibly the result of implanting, the depositing atomshave no surface to align to, resulting in the formation of polysiliconinstead of single crystal silicon.

In one embodiment, the epitaxially formed embedded semiconductor regions25 are stress inducing materials. In some embodiments, the stressinducing materials that are present in the embedded semiconductorregions 25 induce a stress on the channel portion of the semiconductordevice that increases carrier mobility, and therefore increase theswitching speed of the device. In some embodiments, the stress on thechannel of the semiconductor device induced by the embeddedsemiconductor regions 25 has a magnitude ranging from 100 MPa to 1000MPa. In another example, the stress on the channel of the semiconductordevice induced by the embedded semiconductor regions 25 has a magnituderanging from 800 MPa to 1000 MPa.

The stress inducing material that is epitaxially grown in the welltrenches may be a compressive stress inducing material or a tensilestress inducing material. The term “compressive stress inducingmaterial” denotes a material having an intrinsic compressive stress, inwhich the intrinsic compressive stress produces a compressive stress inan adjacent material. In one embodiment, the compressive stress inducingmaterial comprises silicon germanium (SiGe) that is grown atop silicon(Si). Increasing the germanium content increases the lattice dimensionof the silicon germanium and therefore increases the compressive stressthat is induced by the compressive stress inducing material. Typically,the embedded semiconductor regions 25 are composed of compressive stressinducing materials increase the speed of hole charge carriers, andtherefore provide performance enhancements, such as increased switchingspeed, in p-type semiconductor devices.

A number of different sources may be used for the epitaxial depositionof silicon-germanium for the stress inducing material. In someembodiments, the gas source for the deposition of epitaxial SiGe mayinclude a mixture of silane (SiH₄), and germane (GeH₄) gas. The Gecontent of the epitaxial grown SiGe may range from 5% to 60%, by atomicweight %. In another embodiment, the Ge content of the epitaxial grownSiGe may range from 10% to 40%.

The term “tensile stress inducing material” denotes a material layerhaving an intrinsic tensile stress, in which the intrinsic tensilestress produces a tensile stress in an adjacent material. In oneembodiment, the tensile stress inducing material comprises silicon dopedwith carbon (Si:C) that is grown atop silicon (Si). Increasing thecarbon content decreases the lattice dimension of the silicon doped withcarbon (Si:C), and therefore increases the tensile stress that isinduced by the tensile stress inducing material. Typically, the embeddedsemiconductor regions 25 are composed of tensile stress inducingmaterials increase the speed of electron charge carriers, and thereforeprovide performance enhancements, such as increased switching speed, inn-type semiconductor devices. In the embodiments, in which the stressinducing material is composed of epitaxially grown Si:C or carbon dopedsilicon, the carbon (C) content of the epitaxial grown Si:C may rangefrom 0.3% to 5%, by atomic weight %. In another embodiment, the carbon(C) content of the epitaxial grown Si:C may range from 1% to 2%.

As indicated above, the outer edge E1 of the embedded semiconductorregions 25 may be separated from the trench isolation region 10 by adimension W3 ranging from 5 nm to 50 nm. In another embodiment, theouter edge E1 of the embedded semiconductor regions 25 may be separatedfrom the trench isolation region 10 by a dimension W3 ranging from 10 nmto 30 nm. By separating the embedded semiconductor regions 25 from thetrench isolation region 10, the present disclosure substantially reducesor eliminates facet formation in the embedded semiconductor region 25.

Referring to FIG. 3, source and drain regions 30 may be formed in theactive region of the semiconductor substrate 5, and partially extendunder the device replacement gate structure 20. Source and drain regions30 are formed via ion implantation of a p-type or n-type dopant into thesemiconductor substrate 5. As used herein, “p-type” refers to theaddition of impurities to an intrinsic semiconductor that createsdeficiencies of valence electrons. The p-type conductivity semiconductordevices are typically produced within silicon containing substrates bydoping the source and drain region 30 adjacent to the first replacementgate structure 5 a with elements from group III-A of the Periodic Tableof Elements. In a silicon containing substrate, examples of p-typedopants, i.e., impurities, include but are not limited to boron,aluminum, gallium and indium. The term “n-type” refers to the additionof impurities that contributes free electrons to an intrinsicsemiconductor. The n-type conductivity semiconductor devices aretypically produced within silicon containing substrates by doping thesource and drain regions 30 with elements from group V-A of the PeriodicTable of Elements. In a silicon containing substrate, examples of n-typedopants, i.e., impurities, include but are not limited to, antimony,arsenic and phosphorous. In another embodiment, to provide the sourceand drain regions, the embedded semiconductor regions 25 may be in-situdoped. The term “in-situ doped” means that the dopant that provides theconductivity of the source and drain regions is introduced during theepitaxial growth process that forms the embedded semiconductor regions25. The source and drain regions 30 may be activated by activationannealing at this stage of the process or at a later stage of theprocess. Activation anneal may be conducted at a temperature rangingfrom 850° C. to 1350° C.

Still referring to FIG. 3, a hardmask dielectric layer 35 is formed onthe semiconductor substrate 5 having an upper surface that is coplanarwith an upper surface of the replacement gate structures 15, 20. Thehardmask dielectric layer 35 may be blanket deposited atop the entiresemiconductor substrate 5 and planarized. The blanket dielectric may beselected from the group consisting of silicon-containing materials suchas SiO₂, Si₃N₄, SiO_(x)N_(y), SiC, SiCO, SiCOH, and SiCH compounds, theabove-mentioned silicon-containing materials with some or all of the Sireplaced by Ge, carbon-doped oxides, inorganic oxides, inorganicpolymers, hybrid polymers, organic polymers such as polyamides or SiLK™,other carbon-containing materials, organo-inorganic materials such asspin-on glasses and silsesquioxane-based materials, and diamond-likecarbon (DLC, also known as amorphous hydrogenated carbon, α-C:H).Additional choices for the blanket dielectric includes any of theaforementioned materials in porous form, or in a form that changesduring processing to or from being porous and/or permeable to beingnon-porous and/or non-permeable.

The hardmask dielectric layer 35 may be formed using a depositedprocess, such as chemical vapor deposition (CVD). Variations of CVDprocesses that are suitable for forming the hardmask dielectric layer 35include, but are not limited to, Atmospheric Pressure CVD (APCVD), LowPressure CVD (LPCVD) and Plasma Enhanced CVD (EPCVD), Metal-Organic CVD(MOCVD) and combinations thereof may also be employed. The hardmaskdielectric layer 35 may also be deposited using evaporation, chemicalsolution deposition, spin on deposition, and physical vapor deposition(PVD) methods. Following deposition, the hardmask dielectric layer 35may be planarized so that the upper surface of the hardmask dielectriclayer 35 is coplanar with the upper surface of the replacement gatestructures 15, 20. Planarization is a material removal process thatemploys at least mechanical forces, such as frictional media, to producea planar surface. The hardmask dielectric layer 35 may be planarizedusing chemical mechanical planarization (CMP). Chemical mechanicalplanarization (CMP) is a material removal process using both chemicalreactions and mechanical forces to remove material and planarize asurface.

A first photoresist mask 40 is formed over the interface replacementgate structure 15, while an upper surface of the device replacement gatestructure 20 is exposed. A photoresist etch mask (not shown) can beproduced by applying a photoresist layer to the surface of the hardmaskdielectric layer 35, exposing the photoresist layer to a pattern ofradiation, and then developing the pattern into the photoresist layerutilizing a resist developer.

FIG. 3 further depicts one embodiment of removing the sacrificial gateconductor structure 19 of the device replacement gate structure 20 toprovide an opening to gate dielectric 18 of the device replacement gatestructure 20. The sacrificial gate conductor structure 19 is typicallyremoved using a selective etch process that removes the devicereplacement gate conductor 19 selective to the gate dielectric 18, thespacer 17, and the hardmask dielectric layer 35. The etch may be anisotropic etch or an anisotropic etch. The anisotropic etch may includereactive-ion etching (RIE). Other examples of anisotropic etching thatcan be used at this point of the present disclosure include ion beametching, plasma etching or laser ablation. In comparison to anisotropicetching, isotropic etching is non-directional. One example of anisotropic etch is a wet chemical etch.

FIG. 4 depicts one embodiment of forming a functional gate conductor 45of the functioning gate structure 50 within the opening to the gatedielectric 18. The functional gate conductor 45 may be a conformallydeposited layer that is present on the sidewalls of the openings, e.g.,exposed sidewalls of the spacer 17, and on the remaining portion of thegate dielectric 18. In one embodiment, the functional gate conductor 45is composed of at least one of TiAl, TanN, TiN, HfN, HfSi, TiAlN, Ru,Pt, Mo, Co and alloys and or combinations thereof. The functional gateconductor 45 can be deposited using chemical vapor deposition (CVD),atomic layer deposition (ALD), sputtering or plating. In one embodiment,the functional gate conductor 45 is composed of titanium aluminum (TiAl)and is deposited using sputtering. As used herein, “sputtering” means amethod for depositing a film of metallic material, in which a target ofthe desired material, i.e., source, is bombarded with particles, e.g.,ions, which knock atoms from the target, where the dislodged targetmaterial deposits on a deposition surface. Examples of sputteringapparatus that may be suitable for depositing the n-type work functionmetal layer include DC diode type systems, radio frequency (RF)sputtering, magnetron sputtering, and ionized metal plasma (IMP)sputtering.

In addition to physical vapor deposition (PVD) techniques, such assputtering, the p-type work function metal layer may also be formedusing chemical vapor deposition (CVD) and atomic layer deposition (ALD).Although, the functional gate conductor 45 has been described as beingcomposed of a metal, the functional gate conductor 45 may also becomposed of doped silicon, e.g., doped polysilicon.

The metal-containing layer or doped semiconductor material that providesthe functional gate conductor 45 may be deposited to fill the opening tothe gate dielectric 18. The functional gate conductor 45 may beplanarized until an upper surface of the functional gate conductor 45 iscoplanar with an upper surface of the hardmask dielectric layer 35, asdepicted in FIG. 4. In one example, the planarization process isprovided by chemical mechanical planarization (CMP). The functioninggate structure 50 that is provided by the functional gate conductor 45and the gate dielectric 18 is the structure used to control outputcurrent, i.e., flow of carriers in the channel, of the semiconductingdevice, such as a field effect transistor, through electrical ormagnetic fields.

The first photoresist mask 40 may be removed using selective etching,chemical mechanical polishing (CMP) or oxygen ashing.

Referring to FIG. 5, the hardmask dielectric layer 35 is recessed toexpose at least a portion of the sidewalls of the spacers 12, 17 of theinterface replacement gate structure 15, and the device replacement gatestructure 20. The upper surface of the hardmask dielectric layer 35 maybe recessed using an etch that is selective to the interface replacementgate structure 15 and the spacers 17 and the functional gate conductor45 of the functional gate structure 50. A second photoresist mask 55 maybe formed over the functional gate structure 50, while the upper surfaceof the interface gate structures 15 are exposed. The second photoresistmask 55 is similar to the first photoresist mask 40 that is describedabove with reference to FIG. 2. Therefore, the description of the firstphotoresist mask 40 that is described above with reference to FIG. 2 issuitable for the second photoresist mask 55 that is depicted in FIG. 5.

FIG. 6 depicts removing a sacrificial gate conductor structure 14 of theinterface replacement gate structures 15. The sacrificial gate conductorstructure 14 may be removed by an etch that is selective to the hardmask35, the second photoresist mask 55, the spacer 12, and the gatedielectric 13. In some embodiments, the sacrificial gate conductorstructure 14 is removed by an etch process that also removes the gatedielectric 13 and the spacer 12, wherein the etch is selective to thesemiconductor substrate 5, the hardmask layer 35 and the secondphotoresist mask 55, as depicted in FIG. 7. In another embodiment, eachof the sacrificial gate conductor structure 14, the gate dielectric 13,and the spacer 12 are removed independently using a selective etchprocess. In a following process sequence, the hardmask layer 35 and thesecond photoresist mask 55 may be removed.

FIG. 8a depicts one embodiment of a semiconductor device 100 that may beformed using the method described above. In one embodiment, thesemiconductor device 100 includes a semiconductor substrate 5 includingan active region and at least one trench isolation region 10 at aperimeter of the active region, and a functional gate structure 50present on a portion of the active region of the semiconductor substrate5. Embedded semiconductor regions 25 are present in the active region ofthe semiconductor substrate 5 on opposing sides of the portion of theactive region that the functional gate structure 50 is present on. Aportion 6 of the active region of the semiconductor substrate 5separates the outermost edge E1 of the embedded semiconductor regions 25from the at least one trench isolation region 10. In one embodiment, aspacer 12 remaining from the interface replacement gate (also referredto as a “replacement gate spacer”) is present over an interface betweenthe portion of the active region of the semiconductor substrate 5 thatseparates the outermost edge E1 of the embedded semiconductor regions 25from the at least one trench isolation region 10, as depicted in FIG. 8b. Still referring to FIG. 8b , the gate dielectric 13 of the interfacereplacement gate structure may also be present over the interfacebetween the portion of the active region of the semiconductor substrate5 and the trench isolation region 10. One of the gate dielectric 13 andthe spacer 12 may be omitted from the structure depicted in FIG. 8 b.

FIGS. 1-7 depict one embodiment of forming a semiconductor device, suchas the semiconductor device 100 depicted in FIG. 8, using a replacementgate process for forming the functional gate structure 50. FIGS. 9-12depict another embodiment of the present disclosure, that employs a gatefirst process to form the functional gate structure 50 a of thesemiconductor device. Referring to FIG. 9, the method may begin withproviding a semiconductor substrate 5 a including an active region andat least one trench isolation region 10 a at a perimeter of the activeregion, forming at least one functional gate structure 50 a on a portionof the active region that is separated from the at least one isolationregion 10 a, and forming an interface gate structure 15 a on aninterface between the active region of the semiconductor substrate 5 aand the at least one trench isolation region 10 a. The semiconductorsubstrate 5 a, trench isolation region 10 a and the interface gatestructure 15 a that are depicted in FIG. 9 are similar to thesemiconductor substrate 5, trench isolation region 10, and interfacegate structure 15 that are depicted in FIG. 1. Therefore, thedescription of the semiconductor substrate 5, trench isolation region10, and interface gate structure 15 with reference to FIG. 1 is suitablefor the semiconductor substrate 5 a, trench isolation region 10 a andthe interface gate structure 15 a that are depicted in FIG. 9.

The functional gate structure 50 a that is depicted in FIG. 9 iscomposed of a functional gate conductor 45 a over a gate dielectric 18a. The functional gate conductor 45 a may be composed of a similarmaterial as the functional gate conductor 45 that is described abovewith reference to FIG. 4. The gate dielectric 18 a may be composed of asimilar material as the gate dielectric 18 that is described above withreference to FIG. 1. The functional gate structure 50 a may be formedusing a gate first method. Specifically, the material layers for thefunctional gate conductor 45 a and the gate dielectric 18 a may first bedeposited on the semiconductor substrate 10 a to provide a materialstack. Thereafter, the material stack may be patterned and etched toform a gate stack. Spacers 17 a may then be formed adjacent to the gatestack using a method similar to forming the spacer 17 depicted in FIG.1.

FIG. 10 depicts forming embedded semiconductor regions 25 a in theactive region of the semiconductor substrate 5 a between the portion ofthe active region that the functional gate structure 50 a is present onand the portion of the active region at the interface with the at leastone trench isolation region 10 a that the interface replacement gatestructure 15 a is present on. The embedded semiconductor regions 25 adepicted in FIG. 10 are similar to the embedded semiconductor regions 25a described above with reference to FIG. 2. Therefore, the descriptionof the embedded semiconductor regions 25 a that are depicted in FIG. 2are suitable for describing the embedded semiconductor regions 25 a thatare depicted in FIG. 10.

FIG. 11 depicts forming source regions and drain regions 30 a onopposing sides of the portion of the semiconductor substrate 10 a thatthe functional gate structure 50 a is formed on. The source regions anddrain regions 30 a that are depicted in FIG. 11 are similar to thesource and drain regions 30 that are described above with reference toFIG. 3. FIG. 11 also depicts forming a hard mask layer 35 a over theinterface replacement gate structures 15 a and the functional gatestructure 50 a, recessing the hard mask layer 35 a, and forming aphotoresist mask 60 over the functional gate structure 50 a. The hardmask layer 35 a depicted in FIG. 11 is similar to the hard mask layer 35that is depicted in FIGS. 4-6. Therefore, the description of the hardmask layer 35 with reference to FIGS. 4-6 is suitable for the hard masklayer 35 a depicted in FIG. 11. The photoresist mask 60 depicted in FIG.11 is similar to the second photoresist mask 55 that is depicted in FIG.5.

FIG. 12 depicts removing at least a portion of the interface replacementgate structure 15 a. In some embodiments, the sacrificial gate conductorstructure 14 a of the interface replacement gate structure 15 a isremoved by an etch process that also removes the gate dielectric 13 aand the replacement gate spacers 12 a, wherein the etch is selective tothe semiconductor substrate 5 a, the hardmask layer 35 a and thephotoresist mask 60. In another embodiment, each of the sacrificial gateconductor structure 14 a, the gate dielectric 13 a, and the spacers 12 aare removed independently using a selective etch process. In someexamples at least one of the gate dielectric 13 a and the gate spacers12 a remains in the final structure.

The method depicted in FIGS. 9-12 may provide the semiconductor device100 that is depicted in FIGS. 8a and 8b . The gate first processdepicted in FIGS. 9-12 eliminates the requirement of a photolithography,etch and deposition sequence to remove the replace the sacrificial gatestructure 14, 14 a with a functional gate structure, as required by areplacement gate process, such as the process sequence depicted in FIGS.1-7.

In some embodiments, the methods and structures disclosed herein reduceor substantially eliminate the formation of faceting within an embeddedsemiconductor region 25, 25 a such as embedded silicon germanium, byobstructing the contact of the embedded semiconductor region with atrench isolation region 10, 10 a. Further, in some embodiments, byremoving the sacrificial gate conductor structure 14, 14 a from theinterface replacement gate structure 15, 15 a, the present disclosurereduces parasitic capacitance.

While the present disclosure has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the scope and spirit ofthe present disclosure. It is therefore intended that the presentdisclosure not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

What is claimed is:
 1. A method of forming a semiconductor devicecomprising: providing a semiconductor substrate including an activeregion and at least one trench isolation region at a perimeter of theactive region; forming at least one functional gate structure on aportion of the active region that is separated from the at least onetrench isolation region; forming an interface replacement gate structureon an interface between the active region of the semiconductor substrateand the at least one trench isolation region, wherein the interfacereplacement gate structure includes a gate stack of a sacrificial gateconductor structure and a gate dielectric, and a spacer adjacent to thegate stack; forming embedded semiconductor regions in the active regionof the semiconductor substrate between the portion of the active regionthat the functional gate structure is present on and the portion of theactive region at the interface with the at least one trench isolationregion that the replacement gate structure is present on; forming sourceregions and drain regions on opposing sides of the portion of thesemiconductor substrate that the functional gate structure is formed on;and removing at least a portion of the interface replacement gatestructure such that the sacrificial gate conductor structure and thespacer of the interface replacement gate structure are removed, whilethe gate dielectric of the interface replacement gate structure remains.2. The method of claim 1, wherein the semiconductor substrate comprisessilicon, the active region comprises silicon doped with an n-type orp-type dopant, and the at least one trench isolation region comprises anoxide.
 3. The method of claim 1, wherein the forming of the embeddedsemiconductor regions in the active region comprises: etching an exposedportion of the active region between the functional gate structure andthe interface replacement gate structure to form a well trench; andepitaxially forming a semiconductor material having a differentcomposition than the semiconductor substrate within the well trench. 4.The method of claim 3, wherein the semiconductor substrate is comprisedof silicon and the embedded semiconductor regions are comprised ofsilicon germanium.
 5. The method of claim 1, wherein a first portion ofa bottommost surface of the interface replacement gate structuredirectly contacts a topmost surface of the at least one trench isolationregion and a second portion of the bottommost surface of the interfacereplacement gate structure directly contacts a topmost surface of thesemiconductor substrate.
 6. The method of claim 1, wherein the embeddedsemiconductor regions comprise a compressive stress inducing material.7. The method of claim 1, wherein the embedded semiconductor regionscomprise a tensile stress inducing material.
 8. The method of claim 1,further comprising: forming a hardmask dielectric layer on exposedsurfaces of the semiconductor substrate, the hard mask dielectric layerhaving a topmost surface that is located beneath a topmost surface ofeach of the functional gate structure and the interface replacement gatestructure, wherein the hard mask dielectric layer is formed after theforming the source regions and the drain regions and prior to theremoving at least a portion of the interface replacement gate structure;and forming a photoresist over an exposed topmost portion of thefunctional gate structure.
 9. The method of claim 8, wherein the formingthe hard mask dielectric layer comprises: depositing a hard maskdielectric material having a topmost surface that is coplanar with atopmost surface of each of the functional gate structure and theinterface replacement gate structure; and recessing the hard maskdielectric material to provide the hard mask dielectric layer.
 10. Themethod of claim 8, wherein after the removing at least a portion of theinterface replacement gate structure, the topmost surface of the hardmask dielectric layer is located above a topmost surface of a remainingportion of the interface replace gate structure.
 11. A method of forminga semiconductor device comprising: providing a semiconductor substrateincluding an active region and at least one trench isolation region at aperimeter of the active region; forming at least one functional gatestructure on a portion of the active region that is separated from theat least one trench isolation region; forming an interface replacementgate structure on an interface between the active region of thesemiconductor substrate and the at least one trench isolation region,wherein the interface replacement gate structure includes a gate stackof a sacrificial gate conductor structure and a gate dielectric, and aspacer adjacent to the gate stack; forming embedded semiconductorregions in the active region of the semiconductor substrate between theportion of the active region that the functional gate structure ispresent on and the portion of the active region at the interface withthe at least one trench isolation region that the replacement gatestructure is present on; forming source regions and drain regions onopposing sides of the portion of the semiconductor substrate that thefunctional gate structure is formed on; and removing at least a portionof the interface replacement gate structure such that the sacrificialgate conductor structure and the gate dielectric of the interfacereplacement gate structure are removed, while the spacer of theinterface replacement gate structure remains.
 12. A method of forming asemiconductor device comprising: providing a semiconductor substrateincluding an active region and at least one trench isolation region at aperimeter of the active region; forming at least one functional gatestructure on a portion of the active region that is separated from theat least one trench isolation region; forming an interface replacementgate structure on an interface between the active region of thesemiconductor substrate and the at least one trench isolation region,wherein the interface replacement gate structure includes a gate stackof a sacrificial gate conductor structure and a gate dielectric, and aspacer adjacent to the gate stack; forming embedded semiconductorregions in the active region of the semiconductor substrate between theportion of the active region that the functional gate structure ispresent on and the portion of the active region at the interface withthe at least one trench isolation region that the replacement gatestructure is present on; forming source regions and drain regions onopposing sides of the portion of the semiconductor substrate that thefunctional gate structure is formed on; and removing the interfacereplacement gate structure in its' entirety.